Possible two-band superconductivity in PuRhGa5 and CeRhIn5

Measurements of the upper critical field Hc2 of the Pu-based heavy-fermion superconductor PuRhGa5 have been made using a torque magnetometer at temperatures down to 0.6 K and magnetic fields up to 17 T along the principal axes of the tetragonal structure. A linear temperature dependence of Hc2 down to Tc/10 for H||c and to Tc/2 for H||ab is observed. While the data appear to be inconsistent with both purely Pauli limiting or orbital effects governing the upper critical field, the linear T-dependence of Hc2 is well described by a two-band model of superconductivity involving coupled bands of heavy and light electrons. A close similarity between PuRhGa5 and the pressure-induced antiferromagnetic isostructural superconductor CeRhIn5 is also found.